In humans the pancreas is a small elongated organ connected to the duodenum. It is covered in a tissue capsule that partitions the gland into lobules. The bulk of the pancreas is composed of pancreatic exocrine cells, whose ducts are arranged in clusters called acini (singular acinus). The cells are filled with secretory granules containing the digestive enzymes (mainly trypsin, chymotrypsin, pancreatic lipase[?], and amylase) that are secreted into the lumen of the acinus. From there, the secretions accumulate in intralobular ducts and then go to the main pancreatic duct, which drains directly into the duodenum.

Embedded throughout the exocrine tissue are small clusters of cells called the Islets of Langerhans, which are the endocrine cells of the pancreas and secrete insulin, glucagon, and several other hormones. The islets contain three different types of cells — alpha cells (produce glucagon), beta cells (the most numerous, produce insulin), and delta cells (produce somatostatin[?]).